Image reverser for cameras



March 10, 19% w. c. HUEBNER IMAGE REVERSER FOR CAMERAS Filed Feb. 27,1940 4 Sheets-Sheet l INVENTURI W/u/AM C flan/v52,

ATTORNEY.

' March 10; 1942. w. c. HUEBNER v v IMAGE REVERSER FOR CAMERAS FiledFeb. 27, 1940 4 Sheets-Sheet 2 INVENTEIR WILL/AM C. Hum/me,

EWM

ATTURNEY.

March 1942- w. c. HUEBNER IMAGE REVERSER FOR CAMERAS Filed Feb. 27, 19404 Sheets-Sheet 3 FILLIEL v EWM ATTUHNEY.

Patented Mar. 10, 1942 UNITED STATES PATENT OFFICE IMAGE REVERSER FOB.CAMERAS William 0. Huebner, New York, N. Y.

Application February 27, 1940, Serial No. 321,014

3 Claims.

This invention relates to improvements in image reverser for cameras.

In certain arts utilizing photography, and more especially the art ofphotomechanical printing, it is necessary to turn or reverse the imageultimately incorporated on the press plate, dependent upon the method ofprinting used, in order that the impressions taken from the press platewill be read correctly. For instance, inletter press or direct printing,employing the English language, the lines of lettering or readablecharacters must read from right to left and be head up on the printingplate so that, when the ink impressions are obtained on the paper fromthe printing plate by direct contact with the printing plate, theimpressions will read correctly from left to right and be head up.

The same situation also is true in the case of direct gravure printingwhere the lettering on the gravure cylinder or plate must read fromright to left and be head up so that, when impressions are taken bydirect contact, the impressions will read normally, that is, from leftto right and be head up.

' In the case of offset printing, the lettering or readable charactersin the English language must be incorporated on the press plate so as toread and be arranged exactly as they are to appear on the final printedsheet, that is, from left to right and head up. This is due to the fact,as well known to those skilled in the art, that the offset blanket onthe blanket cylinder of the usual offset press, first lifts the inkimage head up but with the lettering in reverse, considred lineally ofthe lines of lettering, and then the ink images of the lettering aretransferred from the offset blanket to the paper with the lettering headup and reading from left to right exactly as on the press plate.

When preparing press plates for offset presses, particularly deep etchpress plates, the usual method is to employ positives of the letteringand other matter to be reproduced and, by contact exposure from suchpositives to the sensitized press plates, obtain on the latter what maybe termed photographic stencils which, after proper development, produceon the press plates, positive images of the lettering or other matter,reading from left to right and positioned head up. Obviously, toaccomplish this result, the letters or other characters on the positiveplate or film which is used for contact exposure on the press plate,must read from right to left and be head up. I

To obtain the proper negatives with the lettering in reverse, forphotoengraving processes, it has been the general practice to employ atriangular section of glass or prism with a reflecting mirror on thelong side thereof which prism is mounted in front of the camera lens.The copy (containing the letters or other readable characters), is thenplaced on a copyboard,

which latter is in a plane parallel to the axis of the lens but locatedeither below or to one side of the lens axis. The image of the copy isthus reflected by the prism mirror surface to and through the lens tothe negative and the letters or other readable characters will, whenviewed from the emulsion side of the negative read from left to right,head up as on the printed sheet. With negatives thus produced, the samemay be laid with the emulsion sides in contact with the sensitized metalplates, the exposures made and the plates then developed and etched forprinting. The images thereby made on the press plates, will read fromright to left, head up as required for direct relief and gravureprinting.

With the prism method of reversing images, however, there are severalserious disadvantages. In the first place, this method requires a socalled right angle camera which is more or less cumbersome andtroublesome. Furthermore, the prism method does not permit of thenecessary degrees of enlargement or reduction often required incommercial practice.

In preparing the positives necessary for deep etch offset printing,hereinbefore referred to, the method heretofore employed and the onewhich is necessary in that type of cameras known as a straight lincamera, that is, a camera wherein the copy, lens, and negative are allarranged in the line of the lens axis with the planes of the copy andnegative parallel to each other and perpendicular to the lens axis, thefollowing method has heretofore been employed. The copy (containing theletters or other readable characters) is placed on the usual copyboardlocated in front of and facing the lens and the negative then exposed inthe usual manner. After development of the negative, the latter is thenplaced on the copyboard in front of and facing the lens and exposedthrough the lens onto av second sensitized plate or film which latterobviously then becomes a positive. While this method permits of thenecessary enlargements or reductions required in commercial work, it issubject to a serious disadvantage, particularly in deep etch offsetwork, in that the positives so made from the negatives by ness that areobtainable from direct contact exposure from-a negative to a positive.

obtaining a reversed negative; the usual or ortho- One object of thisinvention, therefore, is

provide a simple and efficient attachment for a lens of a straight linecamera such that the image of the copy to be reproduced, is so turned onthe negative that a contact positive can Be made from such negative andthe latter in turn used for contact with the sensitized surface of apress platein preparing the press plate for offset printing.

Another object of the invention is to provide a photographic imagereversing device such that, when the device is applied to'or associatedwith a lens of a camera and th copy to be photographed, with the matterthereon readable from left to right head up, is placed in front of andfacing the lens, the image of the copy may be focused on a sensitizedelement in such manner that the resultant image produced on thesensitized element, when viewed from the emulsion side of the negative,will read from left to right and head up.

A further object of the invention is to provide an image reversingattachment for a camera lens which comprises a series of imagereflectors so arranged that the image of a copy located in front of andfacing the lens first impinges upon or is picked up by the incidentreflector of the series and is then reflected successively to the othersof the series and from the last of the series directly to and throughthe lens.

A difliculty commonly experienced in camera work, particularly whereimages must be reflected from one surface to another is the formation ofso called ghost images due to side leakage of light which give faintreflections outside the work area, thus bringing in unnecessary lightand graying the images produced on the negative so that proper contrastof the image is not projected on the ground glass and thus necessitatingmore time exposure around the outer edges than at the center.

To eliminate such ghost images, and particularly where very fine work isrequired, another object of the present invention is to provide simplemeans for trapping such ghost images or intercepting stray light raysaround the work area, which means are readily removable andinterchangeable for others of different characteristics best suited foreach particular job.

Other objects of the invention will more clearly appear from thedescription and claims hereinafter following.

In the drawings forming a part of this specification, Figure 1 is afront elevational view Showing one embodiment of the invention asmounted on the lens of a straight line camera. Figure 2 is a sideelevation of the image reverser shown in Figure 1. Figur 3 is anelevational view of the image reverser shown in Figure 1, but taken fromthe rear side thereof, the image reverser being removed from the lensbarrel. Figure 4 is a vertical sectional view correspondingsubstantially to the line 44 of Figure 1. Figure 5 is a view similar toFigure 1, but with a front plate removed and with the light'interceptoror ghost trap plat shown in section. Figure 6 is a horizontal sectionalview corresponding to the section line 6-6 of Figure 5. Figure 7 is anenlarged detail sectional view, illustrating one of the means forholding a mirror in place. Figures 8, 9 and 10 are schematic viewsillustrating, respectively, the prism method heretofore referred to ofdox method of obtaining a negative in a straight line camera; and themethod of obtaining a re versednegative in accordance with the presentinvention in a straight line camera, the negatives in the several viewsindicating the emulsion sides thereof. Figures 11, 12, 13, 14 and 15 areelevational views of different designs of ghost image trap plates orlight interceptors. Figure 16 is an edge elevational view of one of thelight interceptors shown in Figures 11 to 15. Figure 17 is anelevational view of a light interceptor or ghost image trap plateshowing a light diffuser mounted thereon and Figure 18 is a sideelevational view of the structure shown in Figure 17.

Referring first to the construction illustrated in Figures 1 to 7, I0indicates, conventionally, the barrel of a lens of a straight linecamera and to which, in the form of the invention chosen forillustration, the improved image reverser is adapted to be attached.

The improved image reversing device, as shown, preferably consists of amain metal frame, housing or supporting member A, having a vertical backwall I2 with a suitable opening I3 therein adapting the supportingmember to be slipped over the lens barrel, as best shown in Figures 4and 6, and ,detach'ably secured thereto by thumb nuts I4-I4. Rigid withthe back wall I2 is a plurality of spaced posts I2 adapted to bearagainst the lens barrel base IIl to both steady the attachment andassure its correct position relative to the camera lens.

The supporting member or housing A is formed with a depending chamberdefined by vertical side walls I5-I5 extending parallel to the lens axisand a back wall I6 extending at an angle of 45 to the vertical, as bestshown in Figures 1, 2 and 5. Said chamber has a front rectangularopening I! which faces the usual copyboard of a straight line camerawhich, as hereinbefore explained, has the copyboard in line with theaxis of the lens and facing the latter. As will be seen from Figure 1,said chamber defined by the walls I5I6 is ofiset slightly downwardly andto one side of the lens axis. Disposed within said chamber andpositioned on the inclined back wall I6, is the incident or firstreflecting mirror I3 of the series of mirrors of the image reverser.Said mirror is preferably held in place by a pair of bush pins I9-I9disposed at the side edges of the mirror I8, each of said bush pins, asbest shown in Figure 7, having a stem 20 which extends loosely through acorresponding opening ZI in the wall.- Each bush pin, when brought downinto contact With the mirror, is then adapted to be securely held bytightening up the thumb nut 22, as shown. To facilitate insertion andremoval of the mirror I8, the wall I6 is provided with a detachableflange It at the lower edge, said flange being held in place by thumbscrews I6.

Above the incident chamber defined by the walls I5 and IS, the housingor supporting member A is provided with a wall 23 which is in a. planeparallel to the axis of the lens and is inclined at an angle of 45 tothe vertical and from the outer side of the supporting member toward thetop thereof, as best shown in Figures 1 and 3. Said inclined wall 23 inconjunction with the back wall I2 and vertical front wall 24 defineswhat may be termed the second or intermediate chamber of the housing orsupporting member and is in open communication with the incident orfirst described chamber, as indicated by the opening 25, best shown inFigures 5 and 6. Mounted on the inner side of the inclined wall 23 (seeFigures and 6) is a second or intermediate reflecting mirror 26, thesame being secured in position by bush pins l9-22 in the same manner aspreviously described in connection with the mirror II. The front wall 24is made detachable from the main member A, as by the thumb screws 24, toallow of access to the interior of the member A, as clear from Figures 5and 6. The detachable wall or plate 24 is preferably provided with ahandle 34.

The housing or supporting member A is formed with a third chamber whichis disposed directly in front of the lens, said chamber being defined inpart by the rear vertical wall I2, bottom and top horizontal walls 21and 26 (see Figure 4) and a front wall 29. The latter is preferably madedetachable as by screws 29 and extends in a vertical plane intersectingthe axis of the lens at an angle of 45, as shown. Secured to the innerface of said wall 29 is the third or emitting reflecting mirror 39 ofthe series, the same being secured in the same manner by bush pins asheretofore described in connection with the mirror l8. The third chamberdefined by the walls 12, 21, 26 and 29 is obviously normally inunrestricted communication with the second chamber, as will appear fromFigure 6.

With the image reversing device attached to the camera lens, as shown,and assuming the copy to be on a copyboard in front of and facing thelens, it is evident that an image of the copy will first strike orimpinge upon the mirror 18, as indicated by the dot dash line :c. Fromthe mirror 18, the image will be reflected vertically to the second orintermediate mirror 26, as indicated by the dot dash line 1 From themirror 26, the image is reflected a second time horizontally to themirror 30 as indicated by the dot dash line 2 in Figures 1 and 5, andfrom the mirror 30, the image is finally reflected and emittedhorizontally directly into the lens as indicated by the dot dash linesand arrow m, in Figures 2, 4 and 6, and thence, obviously, through thelens to the sensitized element behind the lens where the exposure ismade.

In carrying out the invention, while it is obvious that the shapes andsizes of the mirrors may be varied, nevertheless in the preferred formof the invention, the first 'or incident mirror 18 is made the largest,the second mirror 26 somewhat smaller, and the third or emitting mirror36 the smallest, so that the maximum amount of image will be picked upby the incident or first mirror i6 and the image gradually reduced andrendered sharper as it is finally emitted from the last mirror 30directly into the lens, and which mirror 30 should be placed as close tothe lens as possible. For lenses of different focus, proportionalchanges of reflecting surfaces may be made so as to utilize the focallength of any lens of given capacity.

To trap or intercept ghost images or stray light rays around the workareas of the reflected images, a trap plate 3| is employed as best shownin Figures 1, 5 and 6. Said plate, which preferably consists of a fiatpiece of sheet metal of generally rectangular outline having a flange 32at one edge thereof for ease of manipulation, is insertable horizontallywithin guide slots 33 provided therefor in the member A. As will beapparent from Figures 5 and 6, the trap plate 31 is located intermediate-the second and third ghost images or stray light beams prior to thereflection of the image onto the last of the refleeting mirrors 3|.

In utilizing the trap plates '31, the same are centrally apertured asindicated at 36, by dotted lines in Figure 2 and full lines in Figuresland 15. In the trap plate 3|, said central aperture is of generallystar shape and its over-all area will be adapted to the particular sizeand capacity of the lens with which the image reverser is beingemployed. In actual practice, it has been found that different styles ofapertures produce better results on different classes of work and inFigures 12, 13 and 14, are illustrated three different styles of trapplates 3|, 31 and 31 having respectively square, diamond and circularapertures 35*, 35 and 35. The sizes and contours of the openings 35, 35,35 and 35 will be varied in in accordance with the requirements inreductions in the image size to be produced on the negative compared tothe size of the image on the copy'; the size of the reproduced imagewhere the same is employed under the rated focal length of the lens; andwhere the ratio is maintained at 1 to 1 but where the size'of the imageis up to or slightly beyond the focal length of the lens.

In Figure 11 is shown a special form of trap plate 31 wherein thecentral aperture 35 has left within it a central section supported byconnector arms 31 which square central section is provided with aplurality of apertures 38. The holes 38 let through a certain portion ofthe light and even out the light field as it strikes the sensitizedsurface of the negative and actual practice mirrors 26 and 30 so as tothus intercept all up when viewed from the emulsion side.

has demonstrated that the reflected images pass through the apertures ofthe trap plate without aberrations of the image beyond the power of thelens and is particularly effective in fine type of work where there is atendency of the light to spread over thin areas and produce only partiallight action and soft edges.

In certain other instances, it has been found desirable to effect awider diffusion of light, in which case a trap plate such as shown inFigures 17 and 18 at 3| is employed. In this trap plate, the centralaperture 35 is preferably similar to that shown in Figure 15 but withcross bars to support the diffuser 39. The latter preferably comprises acentral post-like structure detachably mounted on the cross bars of theplate 31, the post having radiating therefrom a series of sharplytapered or cone-like opaque arms 4|, as shown. With this combination ofghost image trap and light diffuser, the stray light rays around thework area are not only intercepted, but the light is so diffused as toproduce a uniform exposure on the sensitized surface over the entirework area of the image.

Referring to Figure 9, there is there illustrated schematically, theusual complete reversing process which takes place in the orthodox orordinary exposure of a copy to a negative. In said Figure 9, 40indicates conventionally the copy to be reproduced and having thereon aline of lettering or numerals (1940) extending horizontally and readingfrom left to right, as shown. When the image of said copy s transmittedthrough the lens 4|, the image is completely reversed as shown on thenegative 42, that is, the lettering or numerals read from right to leftand are head Heretofore, in the making of positives for deep etchoffset, it has been customary to take such negative 42, place it on thecamera copyboard (corresponding to the copy 40) and project an image ofsaid negative 42 to make a positive.

In Figure 8 is indicated schematically the prism method of obtaining areversed negative. heretofore practiced, the original copy as indicatedat I40 is disposed in a plane parallel to the axis of the lens Illbutoffset to one side thereof, generally horizontally below the lens vaxis. The image of the copy I40 is reflected by the prism 50 through thelens, 'thus producing a negative I42 which, when viewed from theemulsion side, 'has thelettering or numerals reversed from the orthodoxnegative, that is, reads from left to right but is head up as in theorigon the negative reversed from the orthodox neg-.

ative, is obtained with the present invention. In said figure, 240indicates the copy in which the lettering or numerals read from left toright, head up in the usual manner and, after the image thereof has beenreflected by the three mirrors of the reversing device A and through thelens 2, a reversed from the orthodox image is obtained on the negative242, that is, viewed from the emulsion side, the lettering .o r numeralsread from left to right and head up. While in Figure 10, the line of thelettering or numerals in the copy is shown as extending vertically,whereas it appears horizontally in the negative, this is due to the factof the use of the three mirrors and involves merely a matter of routineon the part of the operator as to whether the lines of the copy arearranged vertically and those of the negative horizontally or those ofthe copy horizontally and those of the negative vertically in thecamera.

- With the improved image reverser,it is evident that the same can beused in a straight line .camera and any degree of enlargement orreduction obtained that may be required by commercial considerations,simply by adjusting the copy toward or from the lens as permitted by theusual straight line camera copyboard construction. In

duced as indicated in Figure 10 by the image reverser, it is evidentthat a contact positive may be made directly therefrom for deep etchofiset, thus assuring a positive which is sharp and clear.

While in the preceding description, reference has been made to letters,numerals or readable characters .to be reproduced, nevertheless it willbe evident that the invention applies equally to the reversal ofillustrations or other matter which require correct positioning as toright and left when incorporated on the press plates and whether theprinting is to be done in single color or multiple color. It will alsobe evident that the mirrors are all detachable, and readily accessiblefor cleaning or interchange for others,

and the plates for intercepting the stray light rays or ghost images, aspreviously indicated, are

readily interchangeable. The reverser, as will be apparent from thepreceding description, is compact, light in weight and relativelyinexpensive.

Although there has herein been shown and described what is nowconsidered the preferred manner of carrying out the invention, the sameis merely illustrative and all changes and modifications arecontemplated that come within the scope of the claims appended hereto.

What is claimed is:

1. An image reverser for straight line cameras comprising, incombination: housing means; an optical system consisting of a series ofthree refiecting mirrors of progressively increasing area disposed insaid housing means, said housing means being apertured to engage acamera lens. barrel; means for mounting the smallest mirror closelyfacing the lens and intersecting the lens axis at about forty-fivedegrees when the lens axis is horizontal; means for mounting theintermediate size mirror in a position displaced laterally from butfacing the smallest mirror and parallel to the lens axis; and means formounting the largest mirror facing the intermediate mirror at an angleof about forty-five degrees to the lens axis, said several mountingmeans for said mirrors being also such that, when the smallest mirrorintersects the horizontal lens axis at about forty-five degrees and ispositioned in a vertical plane, said intermediate mirror is positionedat an angle of about forty-five degrees to the vertical and the largestmirror at an angle of about forty-five degrees to the vertical.

2. An image reverser in accordance with claim 1 having ghost image trapmeans carried by and disposed within the housing means and locatedbetween two of said mirrors, said ghost image trap means being aperturedfor the passage of a true image of the copy but with the aperture ofsuch restricted area as to prevent.

passage of ghost images between said two mirrors while the true image istraveling and being transmitted within said housing means.

3. An image reverser in accordance with claim 1 having aperturedlight-diffusing means carried by and disposed within the housing betweentwo of said mirrors.

WILLIAM C. HUEBNER.

